In the textile art the fabric produced is inspected for defects which may occur due to missed stitches apparatus malfunctioning, broken needles, snagging or other causes, and the quality and price of a fabric is affected by the number of defects per unit of fabric length.
Fabric inspection is usually by the human eye, and such manual observation is inconsistent due to human factors such as fatigue, momentary distraction, light variations, and difficulty in observing defects existing in rapidly moving material.
Automatic defect detection apparatus for fabrics has been developed and such devices often use light reflection systems for scanning the fabric face such as shown in U.S. Pat. Nos. 3,160,759; 3,589,816; 3,786,265; 4,057,351; 4,075,498 and 4,103,177.
Prior art light reflection inspection apparatus has been used to terminate the operation of knitting and weaving machines, or to energize an alarm or otherwise indicate the presence of a sensed defect. However, it is not believed that prior art fabric inspection systems of relatively economical manufacture have been capable of recording the number of spaced defects occurring within sequential time intervals whereby the quality of the material may be readily determined, and upon the completion of inspection the fabric readily classified as to its quality.
It is an object of the invention to provide an automatic fabric inspection system which is capable of inspecting flat material moving at high speeds, for instance, inspection speeds to 200 yards per minute are possible and defects as small as 1/16 of an inch diameter may be sensed.
A further object of the invention is to provide a fabric inspection system for flat material wherein inspection may take place on either side of the material, or both sides if a double layered material is being handled.
Another object of the invention is to provide inspection apparatus utilizing reflected light sensors wherein the ability of the fabric to reflect light is automatically sensed and the circuit is automatically adjusted for the light reflective characteristics of the particular fabric being inspected.
Yet another object of the invention is to provide a fabric inspection system utilizing visible and audible alarms wherein the alarms are disabled when the inspection system drive is de-energized, or fabric is not being sensed.
A significant object of the invention is the utilization of a counter in a fabric inspection system which permits the counting of defects only during spaced time intervals wherein an indication of the quality of the fabric is provided.
In the practice of the invention the fabric material being inspected is transferred from one roll to another as a flat web or strip, the "wind up" roll being driven by an electric motor. As the fabric is transferred from the take off roll to the wind up roll defect sensing heads located upon both sides of the fabric and disposed adjacent thereto electronically scan the material throughout its width. The sensing apparatus includes an infrared light source illuminating the portion of the fabric which is scanned by a plurality of infrared sensitive light detectors. The light detectors receive the reflected light from the fabric, and upon a defect occurring a variation in the light reflective characteristics will momentarily occur which will produce a variation in the electronic signal produced by the detector, and this signal is amplified within the circuit of the invention to energize alarms, actuate a counter, or de-energize the wind up roll motor.
The circuit of the invention includes an automatic background sensing control, and means for sensing operation of the wind up roll motor. Upon the motor being de-energized, or the background control sensing the absence of fabric, the circuit is disabled whereby new material may be threaded into the inspection apparatus without triggering the alarms and counter of the system.
Upon the sensing of a defect the resulting electronic signal energizes visual and audible alarms, and also produces an electronic pulse which advances a defect counter. Additionally, the defect signal is imposed upon a relay selectively connectable to the control for the wind up roll motor. The duration of the pulse which operates the counter is adjustable, and during the duration of the counter energizing pulse the occurrence of additional defects are not recorded on the counter. Thus, the counter only records those defects which are spaced from each other by a predetermined distance as regulated by the adjustment of the counter pulse duration, permitting the operator to determine the quality of the fabric being inspected throughout its length. Thus, it is possible to determine how much of the fabric on a roll is usable and defect free. Defects which are adjacent each other do not require the discarding of as much fabric as when the defects are widely spaced on the web and by recording only spaced defects the roll quality is ascertained.
The defect controlled relay connected to the winding roll motor may be selectively abled and disabled whereby the presence of a defect may selectively stop the motor and inspection, or the relay may be rendered ineffective to control the winding roll motor. When the quality of the fabric is to be determined by the counter, and the number of defects occurring between counter actuating pulses, the motor relay is disabled with respect to control over motor operation.